title: Interstitial fluid drainage is impaired in ischemic stroke and Alzheimer's disease mouse models.
abstract: The interstitial fluid (ISF) drainage pathway has been hypothesized to underlie the clearance of solutes and metabolites from the brain. Previous work has implicated the perivascular spaces along arteries as the likely route for ISF clearance; however, it has never been demonstrated directly. The accumulation of amyloid β (Aβ) peptides in brain parenchyma is one of the pathological hallmarks of Alzheimer disease (AD), and it is likely related to an imbalance between production and clearance of the peptide. Aβ drainage along perivascular spaces has been postulated to be one of the mechanisms that mediate the peptide clearance from the brain. We therefore devised a novel method to visualize solute clearance in real time in the living mouse brain using laser guided bolus dye injections and multiphoton imaging. This methodology allows high spatial and temporal resolution and revealed the kinetics of ISF clearance. We found that the ISF drains along perivascular spaces of arteries and capillaries but not veins, and its clearance exhibits a bi-exponential profile. ISF drainage requires a functional vasculature, as solute clearance decreased when perfusion was impaired. In addition, reduced solute clearance was observed in transgenic mice with significant vascular amyloid deposition; we suggest the existence of a feed-forward mechanism, by which amyloid deposition promotes further amyloid deposition. This important finding provides a mechanistic link between cerebrovascular disease and Alzheimer disease and suggests that facilitation of Aβ clearance along the perivascular pathway should be considered as a new target for therapeutic approaches to Alzheimer disease and cerebral amyloid angiopathy.
authors.affiliation: Alzheimer Research Unit, Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 114, 16th St., Charlestown, MA 02129, USA.
authors.forename: Michal
authors.initials: M
authors.lastname: Arbel-Ornath
authors.forename: Eloise
authors.initials: E
authors.lastname: Hudry
authors.forename: Katharina
authors.initials: K
authors.lastname: Eikermann-Haerter
authors.forename: Steven
authors.initials: S
authors.lastname: Hou
authors.forename: Julia L
authors.initials: JL
authors.lastname: Gregory
authors.forename: Lingzhi
authors.initials: L
authors.lastname: Zhao
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Betensky
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Frosch
authors.forename: Steven M
authors.initials: SM
authors.lastname: Greenberg
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Bacskai
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D016229:Amyloid beta-Peptides / Q000378:metabolism; D000818:Animals; D002196:Capillaries / Q000473:pathology; D016657:Cerebral Amyloid Angiopathy / Q000378:metabolism; D004195:Disease Models, Animal; D004322:Drainage; D045604:Extracellular Fluid / Q000378:metabolism*; D007511:Ischemia / Q000378:metabolism / Q000628:therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D020521:Stroke / Q000503:physiopathology / Q000628:therapy*
chemical_list: D016229:Amyloid beta-Peptides